Did any of the fish survive from last night?
When you add dechlorinater to the buckets of water, how do you add it (add some dechlorinater to the bucket then fill it with tap water, aerate for 5 minutes and add to tank)?
-------------------
You have a few heavy metals including aluminium in the water but in low doses. The rest of the water report looks ok. Rain water or reverse osmosis (r/o) might be an idea and see how it goes, even if it's only temporary as a test. If they still die after water changes using rain or r/o, then it's something you are doing.
-------------------
Reverse osmosis units are basically plastic cases with various filter media and membranes in that can remove minerals, chemicals and heavy metals from water. You connect a water source to the inlet of the r/o unit and the water is forced through these different media. At the end of the r/o unit you get two outlet hoses. One hose is for the pure water and the other outlet hose is for the waste water that contains all the impurities. Good r/o units have a 1:1 ratio of pure water vs waste water. So for every one litre of pure water that you get, you get 1 litre of waste water that can be used on the lawn or let it go down the drain. Lesser quality r/o units might have 2:1, 3:1, 4:1 or worse ratios whereby you get 1 litre of pure water and 2, 3, 4 or more litres of waste water.
If you get a r/o unit, get a good quality one with a 1:1 ratio or better if they make them (I don't know of any that are better than 1:1 ratio).
Some r/o units can be fitted to a normal tap and used when needed, others need to be plumbed in, but most just get put on a tap with a threaded fitting.
R/o units produce water slowly, a few litres per hour. Bigger units produce more water per hour but you will need a separate storage container to collect the pure water so you can use it for water changes.
Pure r/o water should not contain any chlorine or chloramine and won't need dechlorinating.
You might have to add some mineral salts to r/o water to increase the GH and KH, depending on what species you keep.